Fatty alcohols and their derivatives have numerous commercial applications, including use as surfactants, lubricants, plasticizers, solvents, emulsifiers, emollients, thickeners, flavors, fragrances, and fuels. In addition, fatty alcohols can be dehydrated to alpha-olefins, which have utility in the manufacture of polymers, lubricants, surfactants, plasticizers, and can also be used in fuel formulations. Currently, fatty alcohols are produced via catalytic hydrogenation of fatty acids produced from natural fat and oil sources, primarily coconut, palm, palm kernel, tallow, and lard. These various sources have different fatty acid compositions; of particular importance is the varying acyl chain lengths that are present. As a consequence, the fatty alcohols derived from these fatty acids also have varying chain lengths. The chain length of fatty alcohols greatly impacts the chemical and physical properties of the molecules, and thus different chain lengths are used for different applications. It is typically necessary to fractionate the mixture of fatty alcohols produced from fats and oils via distillation in order to obtain fractions suitable for specific uses; this is an energy intensive process. Fatty alcohols can also be made by chemical hydration of alpha-olefins produced from petrochemical feedstocks.
Fatty alcohols are also made in nature by enzymes that are able to reduce various acyl-CoA molecules to the corresponding primary alcohols. These enzymes are typically referred to as fatty acyl-CoA reductases, but are also referred to as fatty acid reductases. Acyl-CoA reductases have been shown to occur in numerous kinds of organisms, including, but not limited, to bacteria, plants, fungi, algae, mammals, insects, crustaceans, and worms. In nature, the fatty alcohols produced by acyl-CoA reductases are often incorporated into waxes, cuticles, and other structures that serve as a hydrophobic barrier to water penetration and that can also reduce the risk of pathogen infection. In certain organisms, fatty alcohols can also be incorporated into wax esters for use as storage lipids or as glandular secretions. Non-esterified fatty alcohols are not typically found in substantial quantities in living organisms.
Some acyl-CoA reductases, often referred to as an “alcohol-forming fatty acyl-CoA reductase” generate fatty alcohols directly via a two-step reduction as shown in Reaction [1]. Included in this group is the acyl-CoA reductase JjFAR from the plant Simmondsia chinensis (jojoba) (Metz et al., Plant Physiol 122: 635-644 (2000)). Also included are certain animal acyl-CoA reductases, including those from mice, humans, and nematodes (Cheng and Russel, J Biol Chem 279: 37789-97 (2004), Moto et al., Proc Natl Acad Sci USA 100: 9156-61 (2003)).Acyl-CoA+2NAD(P)H→Fatty Alcohol+2NAD(P)+  [1]
Enzyme-based conversions of acyl-CoA molecules to fatty alcohols can also occur via two distinct enzymes: acyl-CoA is first reduced to fatty aldehyde (Reaction [2]) followed by reduction of the fatty aldehyde to the fatty alcohol (Reaction [3]).Acyl-CoA+NAD(P)H→Fatty Aldehyde+NAD(P)+  [2]Fatty Aldehyde+NAD(P)H→Fatty Alcohol+NAD(P)+  [3]
Included in this group of reductase systems are the acyl-CoA reductase and fatty aldehyde reductase of Acinetobacter sp. M-1 (Reiser and Somerville, J Bacteriol 179: 2969-75 (1997); Ishige et al., Appl Environ Microbiol. 66:3481-6 (2000); Ishige et al., Appl Environ Microbiol. 68:1192-5 (2002)).
The carboxylic acid reductases (“CAR” enzymes) also function in the pathway from fatty acids to fatty alcohols. These enzymes reduce free fatty acids to aldehydes using. The aldehyde to alcohol reduction requires a fatty aldehyde reductase or alcohol dehydrogenase.
Acyl-ACP, acyl-CoA, or acyl moieties on other acyl donors can also be converted to fatty aldehydes by fatty acid reductase complexes encoded by the LuxCDE genes of luminescent bacteria. These genes encode a reductase, a transferase, and a synthetase that catalyze the reaction:Fatty Acid+ATP+NADPH→+Fatty Aldehyde+AMP+PPi+NADP+  [4]
It is important to note that acyl-CoA reductases isolated from different sources typically have preferred substrate ranges with respect to acyl chain length, and thus produce fatty alcohols with different chain lengths and thus different properties.
Current technologies for producing fatty alcohols involve inorganic catalyst-mediated reduction of fatty acids to the corresponding primary alcohols. The fatty acids used in this process are derived from natural sources (e.g., plant and animal oils and fats). Dehydration of fatty alcohols to alpha-olefins can also be accomplished by chemical catalysis. The present invention provides methods to create photosynthetic and heterotrophic microorganisms that produce fatty alcohols and alpha-olefins of specific chain lengths directly such that catalytic conversion of purified fatty acids is not necessary. It is anticipated that this biological route will provide product quality and cost advantages.
Published patent applications and patents relating to the subject matter of the invention include WO 2007/136762, “Production of Fatty Acids and Derivatives Thereof”; U.S. Pat. No. 5,254,466, “Site Specific Modification of the Candida Tropicals Genome”; U.S. Pat. No. 5,370,996, “Fatty acyl reductases”; U.S. Pat. No. 5,403,918, “Fatty acyl reductases”; U.S. Pat. No. 5,411,879, “Fatty acyl reductases”; U.S. Pat. No. 5,411,879 “Fatty acyl reductases”; U.S. Pat. No. 5,723,747 “Wax esters in transformed plants”; U.S. Pat. No. 6,143,538, “Fatty acyl-CoA reductase”; U.S. Pat. No. 7,332,311 “Fatty acyl-CoA: fatty alcohol acyltransferases”; JP Patent 2002223788, “Manufacture of alcohols with plant transformed with acyl reductase gene”; and JP 2004290148, “Pheromone gland-specific fatty-acyl reductase of the silkmoth, Bombyx mori”. 
Published literature having subject matter related to the present application includes the following:
Black, P. N., Zhang, Q., Weimar, J. D., DiRusso, C. C. (1997) Mutational analysis of a fatty acyl-coenzyme A synthetase signature motif identifies seven amino acid residues that modulate fatty acid substrate specificity. J. Biol. Chem. 272: 4896-4903.
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Cheng, J. B. and Russell, D. W. (2004) Mammalian Wax Biosynthesis: I. Identification of two fatty acyl-coenzyme A reductases with different substrate specificities and tissue distributions. J. Biol. Chem. 279:37789-37797.
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Moto, K., Yoshiga, T., Yamamoto, M., Takahashi, S., Okano, K., Andoa, T., Nakata, T. and Matsumoto, S. (2003) Pheromone gland-specific fatty-acyl reductase of the silkmoth, Bombyx mori. Proc. Natl. Acad. Sci. USA 100:9156-9161.
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Wahlen, B. D., Oswald, W. S., Seefeldt, L. C., and Barney, B. M. (2009) Purification, Characterization, and Potential Bacterial Wax production Role of an NADPH-Dependent Fatty Aldehyde Reductase from Marinobacter aquaeolei VT8. Appl. And Environ. Microbiol. 75: 2758-2764.